1. Field of the Invention
This invention relates to operating voltages during normal and lower power consumption states on circuit boards implementing semiconductor chips.
2. Background
Computers historically have operated at two power consumption states: OFF and ON. During the ON state, the computer operates at a maximum specified voltage levels and maximum power consumption. During the OFF state, the computer is not operational, the voltage levels are zero, and power consumption is zero. With the advent of laptop computers and energy efficient desktop computers, computer designers have introduced the concept of lower power consumption states during regular computer operation. To establish lower power consumption states, unused portions of circuitry are shut off or put into a standby state. In some low power consumption states, the computer microprocessor clock is slowed down or turned off.
The microprocessor is a large power consumer in a computer, consuming more power and drawing more current at higher speeds. The microprocessor typically can operate at various voltages, consuming more power at higher voltage levels. The microprocessor is very sensitive to voltage levels. The higher the voltage level, the faster the operating speed capability and the higher the power consumption. The lower the voltage level, the slower the operating speed capability and the lower the power consumption. At voltages below a certain level, the microprocessor malfunctions. Microprocessor manufacturers strive to lower power consumption by lowering operating voltage levels while optimizing the operating speed capability of microprocessors.
During the changing of a computer from one power consumption state to another, the power consumption changes instantaneously. Stopping or starting the microprocessor clock changes the power requirements on a computer circuit board instantaneously. Current draw from the microprocessor may change from as little as 0.3 amps to as much as 10 amps in one microprocessor clock cycle. The power supply cannot instantaneously increase or decrease power output and may take several microseconds to regulate the power output. As a result, after a change in power consumption state of the computer, the voltage level output from the power supply experiences large dips and rises due an increase or decrease of current draw. When the state of the computer changes from a higher to lower power consumption rate, the voltage level rises as the current draw from the computer decreases. The power supply decreases the power output and the voltage level returns to normal. When the state of the computer changes from a lower power consumption rate, the voltage level falls as the current draw from the computer increases. The power supply increases the power output and the voltage level returns to normal. At times, the voltage level may dip below the minimum operating voltage of the microprocessor, causing the computer to malfunction. When the voltage drops below the minimum operating voltage of the microprocessor, internal timing requirements may not be met causing incorrect data to be fetched from cache or other such errors.
To keep the voltage level within an operational range, computer designers have added large capacitors to computer circuit boards. The large capacitors are expensive and use valuable circuit board space, making them an undesirable solution.
A method of preventing computer malfunction during a change of power consumption states while reducing capacitor requirements is disclosed. Prior to a transition from a lower power consumption state to a higher power consumption state the voltage level supplied by the power supply is increased such that when the computer returns to the higher power consumption state, the voltage level remains within minimum operating limits.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.